T: Now look at the picture. Where is the camera? S: It's on the desk. T: Where was it a moment ago? S: It was in the bookcase a moment ago. (突然“砰”的一声,一位学生不小心把文具盒掉在地上,全班学生目光都投向声响处,他们禁不住拍着胸脯说:“吓死了!吓死了!”原来安静的课堂热闹了起来。教师看着那名学生非常生气,忍不住斥责了几句。然后教师花了好大一会功夫才让课堂恢复平静,继续接着刚才的话题展开教学。)